If you have lights, I'd start a lot earlier.....4 am. Sunrises at 6:30 there. First light is around 6.
I never figured out how to stay cool when riding hard in hot and high humidity like in Florida. Camelbacks with ice in them helps a bit. There simply is not enough evaporative cooling from sweat and to me that is the problem with high humidty cycling. I have seen riders stuff ice into sock and drape it over their necks. 99F with FLA humidity is reason to slow the pace a bit once it heats up. GL